Distributed in nature Citric acid is widely distributed in nature&comma; found in plants such as lemon&comma; orange&comma; pineapple&comma; currant&comma; raspberry&comma; Grape Juice fruit and animal bones&comma; muscles&comma; blood&period; Citric acid is synthesized with sugar&comma; starch&comma; molasses&comma; grapes and other sugary material fermentation&comma; can be divided into anhydrous and two kinds of pure hydrate&period; Citric acid is a colorless transparent crystal or white powder&comma; odorless&comma; has an attractive acidity&period; Translucent colorless crystals obtained from concentrated aqueous solution of heat in the anhydrous melting point is 153ºC&period; Translucent colorless crystals obtained from water solution is a water softening&comma; the density is 1&period;542&period;75 at about 100ºCmelting&period; One water compoment can loss water in dry air&period; It is a strong organic acid&period; It is soluble in water&comma; ethanol and ether&period; Used in the manufacture of drugs&comma; soda&comma; candy&comma; also used as a metal cleaning agent&comma; mordant&period;Many kinds of fruits and vegetables&comma; especially citrus fruits contain more citric acid&comma; especially lemon and lime -- they contain a lot of citric acid&comma; after drying&comma; the content is up to 8&percnt; &lpar;in the juice content is about 47 g &sol; L&rpar;&period; In the citrus fruits&comma; the content of citric acid is between 0&period;005 mol &sol; L of orange and grape and 0&period;30 mol &sol; L of lemon and lime &period; The content changes different from cultivars and plant growth&period;